fields

Adding extra fields does take up space even if the fields are empty.
To be precise each text field takes up a minimum of 4 bytes, so if you have 10,000 records and you add 50 new, but blank, text fields, you've bumped up your database size by
4 bytes per blank text field
times
10000 fields
times
50 text fields
which is 2 megabytes.
For more information on the space take